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NASA Discovers a Soggy Secret of El Nino
NASA-funded researchers have discovered El Nino’s soggy secret. When scientists identified rain patterns in the Pacific Ocean, they discovered the secret of how El Nino moves rainfall around the globe during the life of these periodic climate events when waters warm in the eastern Pacific Ocean. The results may help scientists improve rainfall forecasts around the globe during the life of an El Nino, and may also offer new insights into how an El Nino develops. The findings were highlighted in a paper authored by Scott Curtis of the University of Maryland - Baltimore County, Baltimore, Md., and Bob Adler, of Goddard Space Flight Center, Greenbelt, Md. The study appeared in a recent issue of the American Geophysical Union’s Journal of Geophysical Research.
In an effort to predict and understand the effects of El Nino, most scientists focus on seasonal changes in rainfall patterns, like where and when rain falls during winter. This study takes a different approach by first looking at the evolution of rainfall over the geographic area of the Pacific, which has the power to change the global winds and re-direct rainfall patterns around the world. Curtis and Adler found a significant pattern of alternating rainfall for El Ninos since 1979, with wetness in eastern China, dryness over Indonesia and wetness in the south Indian Ocean and Australia.
They noted that this pattern swings eastward as the El Nino weakens. As El Nino weakens, rainfall patterns alternate from one area to another. In the eastern Pacific, there is wetness on the Equator, dryness off the coast of Mexico, and wetness off the coast of California. The traditional view of El Nino based on seasonal rainfall patterns obscures these relationships. El Nino events, like individual thunderstorms, differ in intensity, lifespan, rainfall, and other characteristics, making them difficult to quantify. So, Curtis and Adler had to set parameters to define El Ninos based on rainfall that occurs in the equatorial Pacific. They looked at the periods before rainfall began, when the El Nino started, peaked, faded, and after it ended. They also identified areas around the globe that were consistently wet or dry during each El Nino evolution stage.
Curtis and Adler utilized global rainfall datasets developed from satellites and rain gauges from all over the world, which are part of the Global Precipitation Climatology Project under the Global Energy and Water Cycle Experiment (GEWEX), a project heavily supported by NASA. Data from the Tropical Rainfall Measuring Mission (TRMM) satellite, used in this study, will also help ensure the accuracy of satellites used by the National Oceanic and Atmospheric Administration (NOAA) and Department of Defense. TRMM is a joint NASA/Japanese Space Agency mission to study tropical rainfall and its implications for climate. Each day, the TRMM spacecraft observes the Earth's equatorial and tropical regions.
In the future this kind of study will help pinpoint where an El Nino will generate floods, droughts, and changes in rainfallaround the globe. This information will be extremely useful once NASA’s Global Precipitation Measurement mission, currently in formulation, launches sometime after 2007. This NASA funded work addresses a number of NASA’s Earth Science Enterprise research strategies, including how variations in local weather, precipitation and water resources are related to global climate variation, in this case caused by El Nino. By recognizing global rainfall patterns associated with El Nino and by better understanding the impacts of El Nino, researchers may be able to better understand and predict these climate variations. For more information contact: Rob Gutro Chip Rose Harvey Leifert For information the about various programs mentioned above on the Internet, visit:
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